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Abstract:

Photoelectron spectroscopy is an excellent experimental technique for directly determining the energy and momentum of electrons at solid surfaces and is widely used as a standard technique in solid-state physics. It is quite natural to think that laser technology can make a significant contribution to this analytical technique, and in fact, although still in the minority in number, laser-excited photoemission spectroscopy has become one of the core components of photoemission spectroscopy. Two-photon photoemission spectroscopy is the main stream of laser-based photoemission spectroscopy, which can provide spectroscopic data on unoccupied electronic structures with high temporal resolution, which is difficult to achieve with  conventional photoemission spectroscopy.

In this talk, I will show that two-photon photoemission spectroscopy can also achieve high energy resolution (at the expense of time resolution). Especially, this method is powerful for studying spin-orbit couplings such as the Rashba effect, and modulations of electronic structure originating from moiré structures, which have recently been in the spotlight as Twistronics.